concussion repercussions?

AI had a recent MRI of my  brain (without contrast) after I experienced 10 seconds of nausea, light-headedness and a frontal headache. The MRI showed no large vessel stenosis or aneurysm but patchy areas of signal abnormality in subcortical and periventricular white matter of both cerebral hemispheres, mainly in the frontal lobes & periatrial regions. No evidence of infract. Nonspecific white matter lesion. No bleeding. I don't smoke, normal weight and blood pressure, no diabetes, exercise regularly, have eaten a low-fat diet for years. I am 70, female, and have had five concussions in my active life, the last one 20 years ago. Could these be responsible for the findings since no cardiovascular disease seems present and tests for peripheral blood vessel problems in my legs are normal? Carotid artery is clear. If it is a result of concussions, is this condition likely to progress? No current symptoms except frontal headaches occasionally and what seemed to be that mini TIA  recently, as detailed above. Doctor put me on low-dose Zocor and Plavix for now. What is the most likely explanation for these findings and what advice, if any, do you have? Thanks.